This invention concerns a motor vehicle door lock mechanism with a rotary latch that surrounds a locking element in the device's locking position and that is preloaded in the direction of the locking element when the device is in the open position, a locking pawl that is positioned in relation to the rotary latch when in the engagement position in such a way that the rotary latch is prevented from moving in the direction of the open position, and a drive element, which is used to couple a coupling section of the locking pawl and that moves the locking pawl between the engagement position and a release position, at which the locking pawl is not engaged with the rotary latch so that the rotary latch can move in the direction of the open position.
A motor vehicle door locking mechanism of the aforementioned kind is, for example, recognized in DE 10 2007 024 672 Al and is, among other fields, used for tailgates of motor vehicles. Such a motor vehicle door lock comprises a locking element often equipped with a rotary latch and connected to a boot lid as well as a counter part for the lock connected to the body of the vehicle, which could, for example, be in the form of a locking clip or latchbolt. In order to open the tailgate, the user actuates a control mechanism (for example using an electronic key), which causes the tailgate to be opened using a drive element that would preferably be operated by an electric motor. As part of this opening process, a pivotally mounted locking pawl is guided out of the engagement position (at which the locking pawl usually connects with the rotary latch as forced by a spring mechanism) by the drive element to such an extent that it reaches the release position and the rotary latch is no longer engaged, which allows for a rotary motion of the rotary latch out of the locking position and in the direction of the opening position. The movement of the locking pawl from the engagement position to the opening position takes place in opposition to the force exercised by a spring element, due to the fact that the locking pawl is spring-loaded and pre-stressed in the direction of the locking position. The motor of the drive element therefore has to be dimensioned accordingly, though the smallest possible and therefore less powerful ones are preferred, which then reduces the power requirements of the door locking mechanism again.
The fact that the tailgate is generally pre-stressed in the direction of a seal when in the locking position generally has to be considered when further developing an already advanced motor vehicle door locking mechanism. This “pre-stress” refers to the circumstance that the seal back pressure caused by the flap seal counteracts the closing of the vehicle's rear lid. That is the reason why there is a higher pressure in the opening direction of the tailgate due to the compressed nature of the tailgate's seal. If the locking pawl is no longer engaged with the rotary latch, the pressure that has built up due to the sealing in the form of a so-called “discharge blow” and the tailgate suddenly and abruptly moves towards the opening direction, which negatively manifests itself as an audible opening sound (that could be interpreted as an adverse effect on the perceived comfort of the mechanism or the vehicle as a whole).
In addition, the locking element positioned in the rotary latch trap of the rotary latch when in the locking position can cause undesired rattling noises due to intended tolerances, which has an adverse effect on the perceived comfort, similar to the opening sound. The invention is based on the task of finding a solution that provides a reliable and compact motor vehicle door locking mechanism that is both simple and cost-effective to construct as well as functions using merely a low-power motor while at the same time ensuring that the noise development of the provided locking function is, overall, reduced to a minimum.
With a motor vehicle door lock of the previously described type, these problems are solved, in accordance with the invention, by only exercising a force on the locking pawl while it is in the engagement position and by ensuring that this force keeps the locking pawl engaged with the rotary latch.